What is the equivalent resistance between points a and b in the figure?

Solution

3Ω and 2Ω are in series
R
1
​
=3+2=5Ω

R
2
​
=30Ω

6Ω and 4Ω are in series
R
3
​
=6+4=10Ω

R
1
​
, R
2
​
and R
3
​
are connected in parallel

R
1
​
=
R
1
​

1
​
+
R
2
​

1
​
+
R
3
​

1
​
=
5
1
​
+
30
1
​
+
10
1
​
=
30
10
​

R=3Ω